• Title/Summary/Keyword: phase-shift technique

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Application of Forced Oscillation Technique for Pitch Dynamic Stability Derivatives of a Missile Model (미사일 모델의 피치 동안정미계수 측정을 위한 강제진동기법의 적용)

  • 김승필;조환기;백승욱
    • Journal of the Korea Institute of Military Science and Technology
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    • v.3 no.2
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    • pp.81-87
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    • 2000
  • This paper presents an application of forced oscillation technique to measure pitch dynamic stability derivatives of a missile model in the low speed wind tunnel. The missile model is oscillated by D.C. electric servomotor with constant amplitudes and frequencies. Phase shift is determined as the difference of peak values between input and output signals from the dynamic stability balance installed at the center of gravity of the model. Stability derivatives were calculated by using phase shifts, amplitudes, forcing moments and input frequencies. Test results show the proper usage of the force oscillation technique with good damping effects.

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Defect Inspection of Phase Shift Photo-Mask with Digital Hologram Microscope (디지털 홀로그램 현미경을 이용한 위상차 포토마스크 결함 측정)

  • Cho, Hyung-Jun;Lim, Jin-Woong;Kim, Doo-Cheol;Yu, Young-Hun;Shin, Sang-Hoon
    • Korean Journal of Optics and Photonics
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    • v.18 no.5
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    • pp.303-308
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    • 2007
  • We report here on the application of a digital holographic microscope as a metrology tool for the inspection and the micro-topography reconstruction of different micro-structures of phase shift photo-mask (PSM). The lithography by phase shift photo-mask uses the interference and the pattern of the PSM is not imaged by general optical microscope. The technique allows us to obtain digitally a high-fidelity surface topography description of the phase shift photo-mask with only one hologram image acquisition, allowing us to have relatively simple and compact set-ups able to give quantitative information of PSM.

Non-Contacted Strain Analysis by Dual-beam Shearography (변형 해석을 위한 Dual-beam Shearography)

  • 김경석;정성욱;장호섭;최태호
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2002.10a
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    • pp.400-403
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    • 2002
  • This paper presents a shearographic technique for measuring in-plane strains. During the measurement, the test object is illuminated alternately with two laser beams, symmetrically with respect to the viewing direction. Employing a phase shift technique, the phase distributions due to object deformation for each beam are obtained separately. The difference of the two phase distributions depicts the derivative of in-plane surface displacements. The technique is equivalent to a system of many strain gages.

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Double Encryption of Image Based on Scramble Operation and Phase-Shifting Digital Holography (스크램블 연산 및 위상 천이 디지털 홀로그래피 기반 영상 이중 암호화)

  • Kim, Cheol-Su
    • Journal of Korea Society of Industrial Information Systems
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    • v.23 no.4
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    • pp.13-22
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    • 2018
  • In this paper, double encryption technology of image based on scramble operation and phase-shifting digital holography is proposed. For the purpose, we perform first encryption digitally using scramble operation for the to be encrypted image, and perform phase modulation to the first encrypted image. Finally, we get the secondary encryption information through the interference between the phase-shifted reference wave and phase modulated image. The decryption process proceeds in the reverse order of the encryption process. The original image is reconstructed by digitally decoding the two encrypted images through a phase shift digital holography technique that appropriately performs arithmetic processing, phase-demodulating and then using the encryption key information used in the scramble operation. The proposed cryptosystem can recover the original image only if both the key information used in the scramble operation, the distance information used in the phase shift digital holography technique, and the wavelength of the light source are known accurately.

$\pi$/4 shift QPSK with Trellis-Code in Rayleigh Fading Channel (레일레이 페이딩 채널에서 Trellis 부호를 적용한 $\pi$/4 shift QPSK)

  • 김종일;이한섭;강창언
    • The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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    • v.3 no.2
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    • pp.30-38
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    • 1992
  • In this paper, in order to apply the $\pi$/4 shift QPSK to TCM, we propose the $\pi$/8 shift 8PSK modulation technique and the trellis-coded $\pi$/8 shift 8PSK performing signal set expansion and set partition by phase difference. In addition, the Viterbi decoder with branch metrics of the squared Euclidean distance of the first phase difference as well as the Lth phase difference is introduced in order to improve the bit error rate(BER) performance in differential detection of the trellis-coded $\pi$/8 shift 8 PSK. The proposed Viterbi decoder is conceptually the same as the sliding multiple de- tection by using the branch metric with first and Lth order phase difference. We investigate the performance of the uncoded .pi. /4 shift QPSK and the trellis-coded $\pi$/8 shift 8PSK with or without the Lth phase difference metric in an additive white Gaussian noise (AWGN) and Rayleigh fading channel using the Monte Carlo simulation. The study shows that the $\pi$/4 shift QPSK with the Trellis-code i. e. the trellis-coded $\pi$/8 shift 8PSK is an attractive scheme for power and bandlimited systems and especially, the Viterbi decoder with first and Lth phase difference metrics improves BER performance. Also, the next proposed algorithm can be used in the TC $\pi$/8 shift 8PSK as well as TC MDPSK.

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High-speed, High-resolution Phase Measuring Technique for Heterodyne Displacement Measuring Interferometers. (헤테로다인 변위 측정 간섭계의 고속, 고분해능 위상 측정)

  • 김승우;김민석
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2002.05a
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    • pp.203-206
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    • 2002
  • One of the ever-increasing demands on the performances of heterodyne interferometers is to improve the measurement resolution, of which current state-of-the-art reaches the region of sub-nanometers. We propose a new scheme of phase-measuring electronics that reduces the measurement resolution without further increase in clock speed. Our scheme adopts a super-heterodyne technique that lowers the original beat frequency to a level of 1 MHz by mixing it with electrically generated reference signal. The technique enables us to measure the phase of Doppler shift with a resolution of 1.58 nanometer at a sampling rate of 1 MHz. To avoid the undesirable decrease in the maximum measurable speed caused by the lowered beat frequency, a special from of frequency up-down counting technique is combined with the super-heterodyning. This alloys performing required phase unwrapping simply by using programmable digital gates without 2$\pi$ ambiguities up to the maximum velocity of 2.35 m/s.

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An Analysis of ZVS Phase-Shift Full-Bridge Converter's Small Signal Model according to Digital Sampling Method (ZVS 위상천이 풀브릿지 컨버터의 디지털 샘플링 기법에 따른 소신호 모델 분석)

  • Kim, Jeong-Woo;Cho, Younghoon;Choe, Gyu-Ha
    • The Transactions of the Korean Institute of Power Electronics
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    • v.20 no.2
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    • pp.167-174
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    • 2015
  • This study describes how digital time delay deteriorates control performance in zero voltage switching (ZVS) phase-shifted full bridge (PSFB) converter. The small-signal model of the ZVS PSFB converter is derived from the buck-converter small-signal model. Digital time delay effects have been considered according to the digital sampling methods. The analysis verifies that digital time delays reduce the stability margin of the converter, and the double sampling technique exhibits better performance than the single sampling technique. Both simulation and experimental results based on 250 W ZVS PSFB confirm the validity of the analyses performed in the study.

Transmission Performance of Half-Symbol-Rate-Carrier Offset QPSK Modulation in Band-limited Channels

  • Yeo, Hyeop-Goo
    • Journal of information and communication convergence engineering
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    • v.7 no.2
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    • pp.152-156
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    • 2009
  • This paper examines the BER performance of the recently proposed half-symbol-rate-carrier (HSRC) offset quadrature phase-shift-keying (OQPSK) receiver for high-speed data communication. A modified demodulation technique using a bit-time period signal integration, the bit-error-rate (BER) performance of the HSRC-OQPSK signal improves more than 4dB compared to that of a demodulation technique using a symbol-time period integration. This paper also examines the BER performance of modified demodulation with various band-limited channels modeled using low-pass filters, and the three different data-rate systems are simulated and compared with the performance of the system using the conventional demodulation technique.

A New Soft Switching Technique for Bi-directional Power Flow, Full-bridge DC-DC Converter (양방향 풀-브릿지 DC-DC 컨버터를 위한 새로운 소프트 스위칭 기법)

  • Song, Y.J.;Park, S.I.;Jeong, H.G.;Han, S.B.;Jung, B.M.
    • Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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    • 2005.11a
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    • pp.251-255
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    • 2005
  • This paper proposes a new soft switching technique for a phase-shift controlled bi-directional DC-DC converter. The described converter employs a low profile high frequency transformer and two active full-bridge converters for bidirectional power flow capability. A new soft switching technique is proposed, which guarantees soft switching over wide range (no load to full load) without any additional circuit components. In the proposed switching scheme, the switch pairs in the diagonal position of the converter each are turned on/off simultaneously by the switching signals with a variable duty ratio depending on the phase shift amount, and the converter is operated without freewheeling interval.

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PAPR reduction of OFDM systems using H-SLM method with a multiplierless IFFT/FFT technique

  • Sivadas, Namitha A.
    • ETRI Journal
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    • v.44 no.3
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    • pp.379-388
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    • 2022
  • This study proposes a novel low-complexity algorithm for computing inverse fast Fourier transform (IFFT)/fast Fourier transform (FFT) operations in binary phase shift keying-modulated orthogonal frequency division multiplexing (OFDM) communication systems without requiring any twiddle factor multiplications. The peak-to-average power ratio (PAPR) reduction capacity of an efficient PAPR reduction technique, that is, H-SLM method, is evaluated using the proposed IFFT algorithm without any complex multiplications, and the impact of oversampling factor for the accurate calculation of PAPR is analyzed. The power spectral density of an OFDM signal generated using the proposed multiplierless IFFT algorithm is also examined. Moreover, the bit-error-rate performance of the H-SLM technique with the proposed IFFT/FFT algorithm is compared with the classical methods. Simulation results show that the proposed IFFT/FFT algorithm used in the H-SLM method requires no complex multiplications, thereby minimizing power consumption as well as the area of IFFT/FFT processors used in OFDM communication systems.